Conventionally, an automatic repeat request (ARQ) control function for error correction has been performed in a medium access control (MAC) layer. However, when the error correction is performed by using the ARQ function, a relatively long delay time occurs and complexity of the error correction performance is increased.
Therefore, in order to solve the problems, a HARQ function performed for error correction in a physical layer (PHY) has been suggested. The HARQ function transmits a burst in the PHY, and when receiving a negative acknowledgement (NACK) for the burst transmission (i.e., when an error occurs in the burst transmission), it performs error correction by retransmitting the corresponding burst.
When the ARQ function and the HARQ function are simultaneously performed, delay time and function duplication occur. In addition, in a wireless communication system such as a wireless broadband (hereinafter, referred to as WiBro) system does not define PDU reordering that occurs due to burst retransmission for a HARQ function. Therefore, when the error correction is performed by the HARQ function in the wireless communication system, a problem in which a PDU and a service data unit (SDU) may not be transmitted according to a sequence number may occur if an ARQ function is not supported in a MAC layer. However, it is inappropriate to perform the ARQ function in the MAC layer for a service that requires prompt data transmission due to complexity in operation and generation of delay. In addition, when a function of securing a PDU sequence is added, retransmission time cannot be secured so that system performance may be influenced thereby.
Meanwhile, when the ARQ function is used, a transmitting side transmits an ARQ block within an ARQ window size and additionally transmits an ARQ block within an ACK range so that generation of buffer overflow in a receiving size can be prevented. However, when the ARQ function is not used, the transmitting side can transmit PDUs without radio resource limitation excluding a case that NACK occurs while performing the HARQ function so that the transmitting side retransmits. Thus, the receiving side buffers unorganized PDUs for a predetermined time period for PDU reordering when a HARQ error occurs, and accordingly, the buffer of the receiving side is overflowed so that received PDUs need to be dropped.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.